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      Java基础：集合
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	Posted on <a href="/2017/06/01/Java基础：集合/" class="article-date">
	  <time datetime="2017-06-01T12:28:49.000Z" itemprop="datePublished">June 1, 2017</time>
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<ul>
<li><a href="#集合概述">集合概述</a></li>
<li><a href="#集合继承关系图">集合继承关系图</a></li>
<li><a href="#集合collection的方法">集合Collection的方法</a></li>
<li><a href="#集合collection的remove方法">集合Collection的remove方法</a></li>
</ul>
<!-- /TOC -->
<h3 id="集合概述"><a href="#集合概述" class="headerlink" title="集合概述"></a>集合概述</h3><ul>
<li>集合，集合是java中提供的一种容器，可以用来存储多个数据<ul>
<li>数组的长度是固定的。集合的长度是可变的</li>
<li>集合中存储的元素必须是引用类型数据(基本类型可以使用包装类，Java内部自动帮我们做了拆装箱操作)</li>
</ul>
</li>
</ul>
<a id="more"></a>
<h3 id="集合继承关系图"><a href="#集合继承关系图" class="headerlink" title="集合继承关系图"></a>集合继承关系图</h3><p><img src="http://ww1.sinaimg.cn/large/c55a7aeely1fmeyzdwjidj20nc08wmxf.jpg" alt=""></p>
<ul>
<li>ArrayList的继承关系:<ul>
<li>ArrayList类继承了抽象类AbstractList同时实现接口List，而List接口又继承了Collection接口</li>
<li>Collection接口为集合的最顶层接口</li>
</ul>
</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="class"><span class="keyword">interface</span> <span class="title">List</span> <span class="keyword">extends</span> <span class="title">Collection</span> </span>&#123;</span><br><span class="line">&#125;</span><br><span class="line"><span class="keyword">public</span> <span class="class"><span class="keyword">class</span> <span class="title">ArrayList</span> <span class="keyword">extends</span> <span class="title">AbstractList</span> <span class="keyword">implements</span> <span class="title">List</span></span>&#123;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<ul>
<li>集合继承体系<ul>
<li>我们在使用<code>ArrayList</code>类时，该类已经把所有抽象方法进行了重写。</li>
<li>实现<code>Collection</code>接口的所有子类都会进行方法重写。</li>
<li><code>Collecton</code>接口常用的子接口有：<code>List</code>接口、<code>Set</code>接口</li>
<li><code>List</code>接口常用的子类有：<code>ArrayList</code>类、<code>LinkedList</code>类</li>
<li><code>Set</code>接口常用的子类有：<code>HashSet</code>类、<code>LinkedHashSet</code>类</li>
</ul>
</li>
</ul>
<h3 id="集合Collection的方法"><a href="#集合Collection的方法" class="headerlink" title="集合Collection的方法"></a>集合Collection的方法</h3><ul>
<li>集合Collection的方法,是集合中所有实现类必须拥有的方法</li>
<li><code>Object[] toArray()</code>  <ul>
<li>集合中的元素,转成一个数组中的元素, 集合转成数组   </li>
</ul>
</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">function</span><span class="params">()</span> </span>&#123;</span><br><span class="line">    Collection&lt;String&gt; cet = <span class="keyword">new</span> ArrayList&lt;String&gt;();</span><br><span class="line">    cet.add(<span class="string">"hai"</span>);</span><br><span class="line">    cet.add(<span class="string">"123"</span>);</span><br><span class="line">    cet.add(<span class="string">"456"</span>);</span><br><span class="line">    Object[] objs = coll.toArray();</span><br><span class="line">    <span class="keyword">for</span>(<span class="keyword">int</span> i = <span class="number">0</span> ; i &lt; objs.length ; i++)&#123;</span><br><span class="line">        System.out.println(objs[i]);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<ul>
<li><code>public abstract int size();</code> <ul>
<li>返回泛型集合中有多少个元素</li>
</ul>
</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">Collection&lt;String&gt; collection=<span class="keyword">new</span> ArrayList&lt;String&gt;();</span><br><span class="line">collection.add(<span class="string">"hai"</span>);</span><br><span class="line">collection.add(<span class="string">"jd"</span>);</span><br><span class="line">System.out.println(collection.size()); <span class="comment">// 输出：2</span></span><br></pre></td></tr></table></figure>
<blockquote>
<p>java中的三种获取长度的方式：<br>    <code>length</code>属性：针对数组的长度获取，可以获取一个数组的长度。<br>    <code>length()</code>方法：针对字符串<code>String</code>的，获取字符串中含有多少个字符。<br>    <code>size()</code>方法：针对泛型集合，获取泛型集合中有多少个元素。</p>
</blockquote>
<ul>
<li><code>boolean contains(Object o)</code><ul>
<li>判断对象是否存在于集合中,对象存在返回true</li>
</ul>
</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">function</span><span class="params">()</span> </span>&#123;</span><br><span class="line">    Collection&lt;String&gt; coll = <span class="keyword">new</span> ArrayList&lt;String&gt;();</span><br><span class="line">    coll.add(<span class="string">"hai"</span>);</span><br><span class="line">    coll.add(<span class="string">"jd"</span>);</span><br><span class="line">    <span class="keyword">boolean</span> b = coll.contains(<span class="string">"jd"</span>);</span><br><span class="line">    System.out.println(b);   <span class="comment">//输出：true</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<ul>
<li><code>void clear()</code><ul>
<li>清空集合中的所有元素,集合容器本身依然存在</li>
</ul>
</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">function</span><span class="params">()</span></span>&#123;</span><br><span class="line">    Collection&lt;String&gt; coll = <span class="keyword">new</span> ArrayList&lt;String&gt;();</span><br><span class="line">    coll.add(<span class="string">"hai"</span>);</span><br><span class="line">    coll.add(<span class="string">"jd"</span>);</span><br><span class="line">    System.out.println(coll); <span class="comment">//输出：[hai, jd]</span></span><br><span class="line">    coll.clear();</span><br><span class="line">    System.out.println(coll); <span class="comment">//输出：[]</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<h3 id="集合Collection的remove方法"><a href="#集合Collection的remove方法" class="headerlink" title="集合Collection的remove方法"></a>集合Collection的remove方法</h3><ul>
<li><code>boolean remove(Object o)</code>   ：移除集合中指定的元素</li>
<li><code>boolean removeAll(Collection&lt;?&gt; c)</code> ：删除有元素，集合容器本身还在</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">static</span> <span class="keyword">void</span> <span class="title">function</span><span class="params">()</span></span>&#123;</span><br><span class="line">    Collection&lt;String&gt; coll = <span class="keyword">new</span> ArrayList&lt;String&gt;();</span><br><span class="line">    coll.add(<span class="string">"hai"</span>);</span><br><span class="line">    coll.add(<span class="string">"jd"</span>);</span><br><span class="line">    System.out.println(coll);  <span class="comment">//输出：[hai, jd]</span></span><br><span class="line">    <span class="keyword">boolean</span> b = coll.remove(<span class="string">"jd"</span>);</span><br><span class="line">    System.out.println(b);     <span class="comment">//输出：true</span></span><br><span class="line">    System.out.println(coll);  <span class="comment">//输出：[hai]</span></span><br><span class="line">    coll.add(<span class="string">"jd"</span>);</span><br><span class="line">	System.out.println(coll);  <span class="comment">//输出：[hai, jd]</span></span><br><span class="line">	<span class="keyword">boolean</span> b1 =coll.removeAll(coll);  </span><br><span class="line">	System.out.println(b1);    <span class="comment">//输出：true</span></span><br><span class="line">	System.out.println(coll);  <span class="comment">//输出：[]</span></span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

      
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      <ol class="nav"><li class="nav-item nav-level-3"><a class="nav-link" href="#集合概述"><span class="nav-number">1.</span> <span class="nav-text">集合概述</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#集合继承关系图"><span class="nav-number">2.</span> <span class="nav-text">集合继承关系图</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#集合Collection的方法"><span class="nav-number">3.</span> <span class="nav-text">集合Collection的方法</span></a></li><li class="nav-item nav-level-3"><a class="nav-link" href="#集合Collection的remove方法"><span class="nav-number">4.</span> <span class="nav-text">集合Collection的remove方法</span></a></li></ol>
    
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